Re: [T3] Brakes have me confused!

["Erik Litchy" <litchy@insightbb.com>]

jim napa wanted ~35 with a 5 dollar core.

i was told that the residual pressure was to help overcome the pressure of
the drum springs.
----- Original Message ----- 
From: "Jim Adney" <jadney@vwtype3.org>
To: <type3@vwtype3.org>
Sent: Monday, October 13, 2003 11:36 AM
Subject: Re: [T3] Brakes have me confused!


> On 13 Oct 2003 at 9:49, Erik Litchy wrote:
>
> > ok when i got my car i tried the brakes and they were frozen from lack
of
> > use, actually all the pedals were.  i sprayed penetrating oil on them
and
> > gave them a good kick that freed them.  but upon filling the brake
resivor
> > the fluid leaked from the piston area (even without pressing the pedal).
so
> > i got a reman master and installed it.  same problem, the fluid leaks
from
> > the piston area for some reason.  so i returned it and got another from
napa.
> >  this one was another casting, i thought good.  so I install it
diffrent,
> > leaving off the switches and pour the fluid in unitl no more air comes
out,
> > then screw in the switches.  i had taken out the pushrod off the pedal
> > assembly to make sure it wouldnt be a factor.  the fluid was leaking
before i
> > got to push the rod in.  can the seals be in backward?  is it my error?
> > wrong brake fluid?  does it take the british fluid?  Girling?
>
> It is most likely that the parts you're getting have sat too long on the
shelf
> and have rusted in the bore. The rust pushes the seal lip inward, leaving
room
> for fluid to leak out. Especially on the last one, where you left the
pushrod
> out, I don't think there's anything you could be doing wrong. No special
fluid
> is required.
>
> You really want to clean up the spilled fluid quickly, or it will peel up
the
> paint, leading to rapid rust. It is completely water soluble, so it cleans
up
> easily with water and a sponge, or rag..
>
> > so should i get a 4th master cyl, at this rate it makes me feel like its
> > something im doing, but i have installed masters in other cars and
trucks
> > without inncident.
>
> If you do this again you might want to just open the mouth of the new MC
and
> take the first piston out so you can inspect it there. Reject it right
away if
> it is rusty in the bore. Rusting in storage is a big problem with brake
parts.
>
> If you still have your original ATe MC I can rebuild it, probably for less
than
> what you've been paying for new ones. What does NAPA charge for one of
these? I
> charge $45 to rebuild one, but, in general, I only have parts to rebuild
the
> ATe ones.
>
> > another question how does the rear brake system work?  i know that there
is
> > supposed to be in drum systems some residual pressure around 15 psi?
how is
> > this accomplished?
>
> Older cars certainly did use the residual pressure valves, but none of the
> tandem cylinder type 3s ever have. No residual pressure valves are used in
> these systems, and none are needed.
>
> I've never understood why it might be desirable, but someone on one of the
> newsgroups claimed that some cars have the reservoir lower than the slave
> cylinders. In such a case you could get negative pressure in the slave
> cylinder, which might tend to draw in air around the seal lip. I have a
hard
> time imagining any vehicle built like this, but if someone knows of one,
or of
> any other reason why a residual pressure valve might be needed, I'd love
to
> learn about it.
>
> -- 
> Jim Adney
> jadney@vwtype3.org
> Madison, WI 53711-3054
> USA
>
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